Sampler for gas-liquid mixtures



Aug. 24, 1948.

R. J. S. PIGOTT ETAL SAMPLER' FOR GAS-LIQUID HIXTURES Filed April 16, 1945 ZLwawlof-S R-J. S.PIGOTT CHARLES TAYLOR Patented Aug. 1948 UNITED STATES PATE N'l OFFICE SAMPLER FOR GAS-LIQUID MIXTURES Reginald J. S. Plgott and Charles R. Taylor, gnors to Gulf Research & Development Company, Pittsburgh, Pa., a. corporation of Delaware Application April is, 1945, Serial No. 588,624

' 1 Claim. (Cl. 73422) Pittsburgh, Pa., ass! This invention relates to samplers i'or gas-liq: uid mixtures which tap oil a portion of a flowing stream, with the entrained gas homogeneously distributed therein, but without substantially raising the resistance to fiow or the main stream.

The i'crced movement of liquid through a filled pipe'is resisted at the wall of the pipe and as a result there occurs a. laminar flow which may be 7 samples which accurately reflect the gas-liquid ratio of the mixture.

'Various attempts which. have been made to overcome the dlfllculty contemplate the use of allies or other obstructions which create a turbulence in the stream to causemixing at or immediately upstream of the point where samples are abstracted. These all have the disadvantage that they cause a pressure loss in the system.

The sampler of the present invention permits withdrawal of homogeneous and correct specimens of gas-liquid mixtures by providing a venturi or an orifice for raising the Reynolds number of the stream and thereby producing the desired turbulence for thorough mixing, accompanied by relatively high recovery of the velocity pressure required to produce the higher velocity at the venturi or orifice, as the velocity beyond the sampler is reduced to that normal in the system. Overall pressure drop is thereby minimized. This is an important advantage in the many uses to which the invention may be supplied, a for example in determining the percentage of entrained air in air-oil mixtures existing in aircraft engine lubrication systems during flight. At high altitudes the expansion of entrained air may result in foaming and insufficient delivery of oil to the engine bearings. The relative amounts of air in the oil should therefore be ascertainable during flight for if the amount becomes excessive, destruction of the engine will rapidly follow. In conditioning the mixture for sampling, however, it is im- .portant to impose the least possible pressure loss in the lubricating system, since any increase in pressure loss from the oil supply tank to the lubricating pump reduces the flight ceiling of the airplane.

One of invention stream of the principal objects achieved by our is to provide a sampler for a flowing a gas-liquid mixture which causes demodified sampler shown in mizing pressure drop sired turbulence to break up striations of bubbles in the stream at the point of sampling, while miniacross the sampler. Another object of the invention is to provide a sampler which imposes the least resistance to tube is of an area such as to withdraw a sample point of greatest mixing and at substantially the same velocity as that of the mixture at such point.

A further object of the invention is to provide a sampler which functions to raise the Reynolds number of a flowing stream of gas-liquid mixture and to extract samples at the point of highest Reynolds number.

Other and further objects and advantages of the invention will be apparent from the following description and drawings, in which Figure 1 is a longitudinal sectional view through one form of sampler.

Figure 2 is a view partly in plan and partly in section along the line 22 of Figure 1, of the sampling tube assembly.

--Figure 3 is a longitudinal sectional view of a modified form of sampler, embodying an orifice instead of a venturi. Figure 4 is a view section along the line 44 of Figure 3.

Referring more and first to Figure 1, a venturi III which is coupled to pipe H has a iaired block mounted within it, the block being formed with a boss t3 which proiects through the well of the venturi at a point rearwardly of its throat, and an internal bore into which pipe i4 is fitted. Two smaller downwardly diverging passageways l5 and IS in the block it connect with a' longitudinal passageway II which extends along the axis of the venturi and connects with a tube It, the tapered end of which lies at the point where the stream of mixture flowing through the venturi is substantially at its point of greatest turbulence. It is essential that the sampling tube not only be accurately located but that it be so sized relative to the throat opening of the venturi that the flow of fluids entering the sampling tube is at substantially the same speed as that in the vena contracta of the main stream. Otherwise, if the tube abstracts the sample at a velocity diilering materially from that 0! the main body of the stream, the sample will be incorrect. The same conditions are required for the Figure 3. In this form. a section of pipe 20 which is of the samein-ternal diameter as the connected piping It has a disc partly in plan and partly in,

particularly to the drawings,

forwardly projecting sampling l2 clamped at its joint on the upstream side and this disc is formed with a circular sharp-edged orifice which produces a vena contracta' in the stream at a location about 0.4 to 0.5 of the main pipe diameter from the edge of the orifice. In

in that previously described,-

this construction, as the hired block 23 has internal passages 24, 25 and II leading from a sampling tube 21 to an outlet pipe 28 which in turn discharges into a displacement chamber or other analytical apparatus (not shown). Where installation space is a (actor which must be taken into consideration the orifice type sampler oflers the advantage that it cation system or to any source or gas-liquid mix- 1 ture where it may be desirable to know the percentage of gas entrained in the liquid.

What we claim is: Apparatus for obtaining homogeneous samples of gas-liquid mixtures in flow through a conduit without substantial pressure loss in the conduit therebeyond, comprising an orifice plate for forming a vena contracta in the flowing stream and thereby raising its Reynolds number, a sampling tube having an opening of such dimensions as to make possible sampling at a velocity approaching the velocity of the main stream, said sampling tube extending centrally ot the stream into the vena contractethereof at a point downstream of the orifice approximately one-half the diameter of said conduit, for abstracting samples of the mixture in the same direction and at substantially the same speed as the rate of the main flow at such point of highest turbulence.

REGINALD J. S. PIGO'I'I. CHARLES R. TAYLOR.

REFERENCES CITED The following references are of record in the file of this patent:

l UNITED STATES PATENTS Number Name Date 790,888 Ferris May 30, 1905 1,041,470 Hiller Oct. 15. 1912 2,020,529 Thorsten Nov. 12, 1935 2,322,018 Huber June 15, 1943 2,327,111 Klmmell Aug. 17,1943 2,363,625 Swearingen Nov. 28, 1944 2,380,977 Lewis Aug. '7, 1945 

